RF interference, which is also referred to as “jamming”, sometimes occurs when a CDMA-like system (such as GNSS) receiver operates. Jamming may be caused by various sources such as channel cohabitance, harmonics from mobile phones, satellites, TV, FM radio, radar and hostile sources. Jamming may surreptitiously degrade accuracy of the receiver and damage the integrity of the receiver. An automatic gain control (AGC) circuit in the receiver keeps the receiver in its optimized operating range by detecting the overall strength of the signal and automatically adjusting the gain of the receiver to maintain an approximately constant average output power level. To design the behavior of the AGC circuit, the input signal characteristics must be taken into consideration to minimize the SNR degradation caused by quantization. For example, an AGC unit of a GNSS receiver usually utilizes a specific input signal model such as Gaussian model. When there is jamming incorporated into the input signal, the AGC unit cannot perform well for the predetermined input signal model, which may cause further signal distortion. Similarly, other functions of the receiver, such as signal acquisition ability and navigation accuracy, may also be influenced by the jamming. Therefore, anti-jamming operation is required. However, it is a waste of power if jamming mitigation function is always activated since jamming occurs occasionally. The signaling environment may often be jamming-free. Executing anti-jamming operation during jamming-free period is a significant waste of power. It will be more economic and efficient if the anti-jamming operation is only executed when there is indeed jamming in the input signal. Therefore, an effective jamming detection scheme is necessary.